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NEC has demonstrated a single fibre link – with no repeaters – running at 1.5 terabits per second over 10,000 km. The company says this is the first time that a single laser source has sent a terabit channel over such a distance.

The lab setup achieved an aggregate of 4 Tbps by binding four “superchannels” together using wavelength division multiplexing (WDM), with a spectral efficiency of 3.6 bits per second per Hertz.

The company says optical superchannels use OFDM (orthogonal frequency division multiplexing) to independently modulate phase-locked carriers. The spectral efficiency of such a setup allows each laser to deliver a higher data rate, NEC claimed.

This next bit is quite a mouthful: “optical multi-tone generation, large-core/ultra low-loss fiber, intradyne digital coherent detection, and digital equalization at higher oversampling, along with well-established technologies such as EDFAs and DP-QPSK modulation. The experiment yielded a 2-dB system margin above the hard decision FEC threshold without using processing-intensive MAP or MLSE algorithms.”

The result was published at the recent Asia Communications and Photonics conference in Shanghai.

Higher capacity on transoceanic links is particularly important for countries like Australia and New Zealand, for whom the “tyranny of distance” creates bottlenecks of speed, price and capacity on international connections. ®